The present apparatus relates to energy collecting means, and more particularly to an improved solar energy collector which concentrates, absorbs and transfers heat to a fluid.
The practical, efficient utilization of solar energy has for generations been the object of much effort and study. In recent times, as the hazards of air pollution due to the use of fossil fuels have become apparent, along with the potential hazards of nuclear energy sources, considerable attention has been focused upon devising economical and practical means for collecting energy of solar rays. Even more lately shortages of petroleum products along with the rapidly rising cost thereof has lent new urgency to the search for practical means for making use of solar energy.
To date, although much effort has been expended in the development of prototype and experimental solar energy collecting and storage apparatus, none have attained any degree of practical, economic success. The expense and/or inefficiency of construction of the apparatus so far devised has inhibited the development of practical solar energy collection means. Ordinarily, solar collectors comprise a metallic plate or the like enclosed by a glass cover so that the sun's rays might pass through the glass and heat the metal therebeneath. Energy from the heated metal is then collected by a heat transfer fluid, such as air or water which is passed beneath or over the metal whereby it is heated. The heated fluid is then stored until needed, then pumped through other heat transfer devices, e.g., radiators, which extract heat energy from the fluid.
The principal difficulty with prior art solar energy collection apparatus has been that conductive losses through the glass plates, and convective losses between glass plates, have limited the maximum temperature of the heated metal plate to relatively low values. Typically, such values have been below 150.degree. F. Accordingly, the stored heat transfer fluid can be maintained at no more than 150.degree. F., or thereabouts and usually much less.
A still further difficulty has been that the sun's orientation with respect to the flat plate collectors is at an optimum for only one or two hours in a ten-hour day if the collector temperature is 150.degree. F. and the stored heat transfer fluid temperature is approximately 140.degree. F. Accordingly, for a ten hour period of sunlight, 80% of the available solar energy may not be used.
In order to overcome this problem, inventors have devised various types of reflectors for use in conjunction with heat absorbers. Typically, the reflectors are pivoted or swiveled so as to maintain the sun's rays focused upon the absorptive apparatus. Said reflectors are commonly surfaces of rotation such as sections of spheres or paraboloids. However, the cost and complexity of these movable apparatus, hereinafter termed steerable reflectors, is often prohibitive. Further, like any complex movable object, they are susceptible to wear and breakage so that they decrease the overall reliability of the heating system. Further, additional energy is required to drive these steerable reflectors. Accordingly, it will be appreciated that it would be highly desirable to provide an improved absorptive apparatus which absorbs solar energy with relatively little loss and does not require diurnal tracking of the sun. This is not possible with conventional focusing techniques. The efficiency of the present invention in absorbing diffuse light is much greater than that of focusing collectors.
It is accordingly an object of the present invention to provide an improved absorptive means for use with solar energy collection systems.
Another object of the invention is to provide a solar energy collecting apparatus which is stationary and does not have to be steered.
Yet another object of the invention is to provide a solar energy collecting reflector in combination with an absorptive apparatus which makes full use of the sun's rays over an extended period of time.